In the lower stratosphere "coupling layer" at 100 hPa, GEFS forecasts are very confident of a transition of the zonal-mean zonal winds to a "weak" state (bottom tercile of daily climatology). This favours negative NAO/negative NAM patterns. (3/4) pic.twitter.com/JBtVVy8Mfh

— Dr Simon Lee (@SimonLeeWx) November 12, 2019